Magnetic spherical polyelectrolyte brushes (MSPB) with embedded magnetite nanoparticles in core were successfully synthesized and characterized by dynamic light scattering (DLS), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). At first, oleic acid modified magnetite nanoparticles (MNP) were synthesized by coprecipitation method, and then embedded into polystyrene core by miniemulsion polymerization to obtain magnetic polystyrene latices (MPL). Finally magnetic spherical poly(acrylic acid) (PAA) brushes were synthesized by photoemulsion polymerization. Effects of MNP and acrylic acid (AA) content on the brush structure were studied in detail. The obtained MSPB are narrowly dispersed, pH sensitive, superparamagnetic and redispersible after aggregating by external magnetic field. Magnetic control is thus introduced into nanosized spherical polyelectrolyte brushes to achieve the recovery and controllable delivery. This approach opens a new way for the recoverable and cost-effective applications of spherical polyelectrolyte brushes.